An electric motor is known from DE 28 31 774 C2 with a disc rotor in the flat air gap having a non-ferrous stator winding which is associated at least on one side with a permanent magnetic ring with an axially magnetised segment and on both sides with soft-magnetic flat discs for the magnetic reflux. Coaxial with the rotor shaft is an electrodynamic tachogenerator which is arranged so that the most compact combination possible is produced for the electric motor and tachogenerator.
The known combination of electric motor and tachogenerator includes the coaxial function elements of the electric motor and tachogenerator arranged in a row, whereby each unit is fully functioning per se when the individual function elements are separated from each other.
The use of maintenance-free electronically commutated motors has been problematic, given on the one hand the on-board mains voltage available up to now of 12 V in motor vehicles, and on the other hand the costs for such electronic commutating circuits. With this low voltage, considerable currents have to be forced through the electronic commutation circuit as a result of the power required.
For both mechanically commutated electric motors and electronically commutated electric motors for use with adjusting devices in motor vehicles, a considerable amount of space has to be provided to include the gear parts required for the adjusting devices. In addition, as a result of the markedly different surrounding conditions during operation, and owing to the operating safety required for such drive units, a considerable manufacturing expense is also incurred.